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BACTERIOLOGY > 8 – Corynebacterium, Rhodococcus > Flashcards

8 – Corynebacterium, Rhodococcus Flashcards

1
Q

Microbiology Characteristics

A
  • Biocontainment level 2
  • Aerobic and facultative anaerobes
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2
Q

Corynebacterium characteristics

A
  • Gram-positive clubbed rods
  • Characteristic ‘palisades’ or ‘Chinese letter’
  • Colony morphology is variable
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3
Q

Rhodococcus characteristics

A
  • Gram-positive cocco-bacilli (‘egg shaped’)
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4
Q

Rhodococcus equi on blood agare

A
  • Produces pink colonies
    o Pigment can be enhanced on other differential media
  • Facultative intracellular parasite
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5
Q

Natural Host or Habitat

A
  • Part of normal microbiota (skin, mucous membranes, intestinal tract)
  • Can survive in environment
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6
Q

Corynebacterium pseudotuberculosis

A
  • Survive in environment for up to 55 days
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7
Q

Rhodococcus equi

A
  • Soil organism
    o Feces contaminated soil
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8
Q

Taxonomy

A
  • Oxidative (Rhodococcus) or fermentative (Corynebacterium)
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9
Q

Virulence Factors: C. renale, cystidis, pilosum

A
  • Pilli: attachment
  • Urease: production of ammonia
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10
Q

Virulence factors: C. pseudotuberculosis

A
  • Phospholipase D
    o Essential VF
    o Damage host cell membranes=facilitates spread
    o Cytotoxic: erythrocytes, neutrophils
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11
Q

Virulence factors: R. equi

A
  • Virulence associated proteins (VAPs)
    o Allows organism to survive intracellularly (prevents acidification of phagosome)
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12
Q

Virulence factors: C. diphtheriae: canonical toxigenic infection (model)

A
  • One of the most studied toxins
  • Diphtheria toxin acts by interfering with host cell protein synthesis
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13
Q

Clinical significance: C. pseudotuberculosis (sheep, goats)

A
  • Causes of caseous lymphadentis
  • Pyogranulomatous abscesses of lymph nodes and organs
    o Contain inspissated material (caseous)
  • Highly contagious
  • Difficult to eradicate once herd infected
  • Antimicrobials don’t penetrate into lesions
  • Worldwide distribution
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14
Q

Clinical significance: C. renale group (bovine)

A
  • Infections of bovine urinary tract (C. renale, cystitidis, pilosum)
  • Cystitis
  • Pyelonephritis
  • *maintained in herd by subclinical carriers and diseased animals
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15
Q

Clinical significance: C. renale group (bovine), cystitis

A
  • Infection of urinary bladder
  • Generally, not systematically sick
  • Hematuria
  • Proteinuria
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16
Q

Clinical significance: C. renale group (bovine), pyelonephritis

A
  • Infection of kidney
  • Fever
  • Depression
  • Reduced feed intake
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17
Q

Clinical significance: C. renale group (bovine), subclinical carriers and diseased animals

A
  • Transmission by urine droplets splashing from infected onto vulva of susceptible cow
  • *isolate affected animals=difficult to eradicate from infected herds
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18
Q

Clinical significance: C. renale group (bovine), attachment facilitated by alkaline conditions, inhibited by acid

A
  • Urease producing organism: converts urea into ammonia
  • Urinary acidification may be helpful
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19
Q

Clinical significance: C. renale group (bovine), treatment

A
  • Penicillin
20
Q

Clinical significance: C. renale group (bovine), likelihood of treatment success decreases as disease progresses

A
  • More difficult to eradicate from kidney
  • Prognosis worsens with increasing renal dmage
  • Cull rate=1/3
21
Q

Clinical significance: C. renale (sheep)

A
  • Balanoposthitis (inflammation of penis and prepuce)
    o PIZZLE-ROT
22
Q

Clinical significance: C. renale (sheep), predisposed by high protein diets->high urea concentration

A
  1. Urea converted into ammonia by organism
  2. Ammonia irritates penis
  3. Inflammation and ulceration
  4. Bacteria enter compromised tissues
  5. Scarring over prepuce prevents penile extrusion and breeding
23
Q

Clinical significance: C. renale (sheep), treatment

A
  • Combination of antimicrobials (penicillin) and debriding dead tissue and removing excess wool
24
Q

Clinical significance: corynebacterium (dogs and cats)

A
  • Role of these is unclear
  • Skin infections (C. auriscanis and C. ulcerans)
    o Frequently polymicrobial infections
    o Treatment can be challenging
  • Rare causes of UTI (C. urealyticum)
25
Q

Clinical significance: C. diphtheria (humans)

A
  • Uncommon in developed countries
  • Respiratory diphtheria is most common
    o Diphtheritic pseudo-membrane over pharynx
  • Disease caused by toxigenic strains
  • DPT vaccines
26
Q

Clinical significance: R. equi (horses)

A
  • Severe bronchopneumonia in young foals
    o Chronic suppurative bronchopneumonia
  • Abscessation in older horses (pyogranulomatous pneumonia)
  • Enteric disease: seen in 50% of foals with pneumonia
  • Acquired from environment (soils contaminated with horse feces)
27
Q

Clinical significance: R. equi (horses): enteric disease

A
  • Fecal-oral or swallowing expectorate sputum
    o Usually pneumonia first
  • Multi-focal ulcerative enterocolitis and typhlitis
  • Weight loss, diarrhea and colic
28
Q

Clinical significance: R. equi (horses), ubiquitous on horse farms, so why not more common?

A
  • Not sure
  • Maybe less virulent strains?
  • Management practices?
29
Q

Clinical significance: R. equi (horses), horses infected when inhale virulent strains

A
  • Only VapA+ isolates are virulent in horses
  • Intermediately virulent isolates producing other Vap proteins have been IDed
    o Humans: HIV associated infections
    o Not found in horses
30
Q

Clinical significance: R. equi (horses), prognosis

A
  • Chronic disease: fair
  • Acute: poor
31
Q

Clinical significance: R. equi (horses), treatment

A
  • Antimicrobials is key
  • Rifampin+macrolide type drug
  • *needs drugs that reach high intracellular concentrations
32
Q

Clinical significance: R. equi (horses), management

A
  • Little evidence of preventive measures
  • Clean up manure, avoid crowding, reduce dust, house foals in well ventilated area
33
Q

Clinical significance: R. equi (cats)

A
  • Rarely reported, but increasing (immunocompromised)
  • Causes cutaneous infections
    o Characterized by pyogranulomatous inflammation
    o Typically non-painful and non-febrile (no fever)
  • Abscesses with draining tracts + lesions of parenchymal organs
  • Treatment: surgical drainage + antimicrobials
34
Q

Specimens to collect

A
  • Pus or exudates: C. pseudotruberculosis
  • Mid-stream urine: C. renale group
  • Trans-tracheal wash: R. equi
35
Q

Sample handling

A
  • Swabs should be sent with transport media
  • Do NOT freeze samples
36
Q

Laboratory ID: Corynebacterium

A
  • Standard culture methods (blood agar)
  • Growth may take up to 48hrs
  • Readily IDed biochemically
37
Q

Laboratory ID: Rhodococcus

A
  • May grow better at low temperatures (30 degrees C)
    o Include on history
  • Partially acid-fast
  • Growth may take up to 48hrs
  • Readily IDed biochemically
38
Q

Laboratory ID: C. pseudotuberculosis

A
  • Immunological tests to detect exposure/infection in cases where abscesses are NOT superficial enough to sample OR don’t want to contaminate the environment
39
Q

Laboratory ID: antimicrobial susceptibility test

A
  • No recognized guidelines
  • Interpret with caution
  • Consult your lab!
40
Q

C. pseudotuberculosis: zoonotic

A
  • Abscesses in humans associated with sheep herders
  • Risk during sheering or while performing necropsy
41
Q

C. renale: zoonotic

A
  • low risk to human health
42
Q

Toxigenic C. ulcerans: zoonotic

A
  • Causes cutaneous diphtheria in people
43
Q

R. equi: zoonotic

A
  • primarily in immunocompromised patients
44
Q

C. pseudotuberculosis treatment options

A
  • Intracellular infections: antimicrobial therapy difficult
  • Control measures depend on prevalence
45
Q

C. pseudotuberculosis treatment options: control measures

A
  • Low prevalence: stamp out (Ex. cull)
  • High prevalence: minimize disease impact
46
Q

C. spp. are intrinsically resistant to

A
  • Fosfomycin
    Possible relevant for UTI treatment in companion animals
47
Q

Rhodococcus treatment options

A
  • Think MLSbK + rifampin
  • Intrinsic penicillin, ampicillin and cephalosporin resistance

BACTERIOLOGY (19 decks)

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